The invention relates to color film and to a method of forming an image by scanning the film.
The great majority of color photographs today are taken using chromogenic color film, in which color-forming couplers, which may be incorporated in the film or present in the processing solution, form cyan, magenta and yellow dyes by reaction with oxidized developing agent which is formed where silver halide is developed in an imagewise pattern. Such films require a development process which is carefully controlled in respect of time and temperature, which is usually followed by a silver bleaching and a fixing step, and the whole process typically takes several minutes and needs complex equipment.
Gasper et al, in U.S. Pat. No. 5,420,003, disclose a photographic color film which employs black-and-white developed color records separated by fluorescent or emissive interlayers. The film offers rapid and simple processing, although its structure of superimposed color records means that processing chemicals have to diffuse a considerable distance down through the various coated layers before they can reach the emulsion layer nearest the base, which increases the time required to process the film. Care must also be taken when altering any of the processing conditions to ensure that all three color records are affected in a similar way, otherwise the color balance of the film may be adversely affected. After opto-electronic scanning, the optical densities in the separate color records are calculated by taking differences and performing other appropriate mathematical operations, after which an image of the original scene is reconstructed.
Simons in U.S. Pat. No. 5,418,119 discloses a photographic color film which employs black-and-white developed color records separated by interlayer units which are capable of passing light through to an underlying emulsion layer unit and are capable, after photographic processing, of reflecting light in at least one wavelength region. The imagewise exposed photographic element can be photographically processed to produce a silver image in each of the emulsion layer units, and can be reflection scanned utilizing reflection from the interlayer unit to provide a first record of the image information in one of the two emulsion layer units and can be reflection or transmission scanned to provide second and third records of the image information in the other two emulsion layer units. The first, second and third records can be compared to obtain separate blue, green and red exposure records. This film suffers from difficulties similar to those of the film disclosed by Gasper et al, in that processing chemicals have to diffuse a considerable distance down through the various coated layers before they can reach the emulsion layer nearest the base, which increases the time required to process the film, and also means that care must be taken when altering any of the processing conditions to ensure that all three color records are affected in a similar way, otherwise the color balance of the film may be adversely affected.
The invention aims to provide a film and a method for taking color photographs which use digital image processing to display or print the image and require only a very simple, rapid and reliable chemical processing step.
The object of the digital image processing is to provide a color image of higher quality than would otherwise be achievable by, for example, an optical print of the color filter array (CFA) film. The primary aim of the image processing is to remove those artifacts in the scanned image data that result from the inclusion of a color filter array in the film, in particular colored noise in the case of a film with a random or irregular CFA, or colored structure in the case of a film with a regular CFA. Loss of color saturation may also be corrected.
According to the present invention there is provided a color film for recording an image comprising a support layer, a layer formed of a color filter array having at least three spectrally distinguishable types of color element, and at least one emulsion layer, the film further including means for emitting or reflecting light which has been modulated by the color filter array but has not been substantially modulated by the image pattern formed in the at least one emulsion layer.
The means may be a reflective, scattering or fluorescent layer interposed between the color filter array and the emulsion layer. Alternatively, the means may be reflective, scattering or fluorescent material within the color filter array layer, in the space between the color elements of the array and/or within the color elements themselves.
The color filter array itself may be either regular or random.
The present invention further provides a method of forming a color image of a scene from an imagewise exposed photographic film, the film comprising a support layer, a layer formed of a color filter array having at least three spectrally distinguishable types of color element and at least one emulsion layer, the film further including means for emitting or reflecting light which has been modulated by the color filter array but has not substantially been modulated by the image pattern formed in the at least one emulsion layer, the method comprising developing the image of the scene formed in the emulsion layer, electro-optically scanning the resultant image through the color filter array, electro-optically scanning the color filter array by light which has not been substantially modulated by the image formed in the emulsion layer, and digitally image processing the two sets of scanned image information to give an electronically coded representation of the scene.
The color filter array may be scanned by light which has been reflected or emitted from the color filter array or from a layer between the color filter array and the emulsion layer.
The film and method of the present invention provides a light sensitive emulsion layer unit, which may comprise one or more layers, which is sensitive to light which has passed through each or all of the different color elements of the color filter array, so that the image information for each color record is recorded in the emulsion layer unit. This unit can be thinner than the three separate color-sensitive emulsion layer units disclosed in the prior art and so provides more rapid photographic processing. Also, variations to the photographic process, whether inadvertent or intentional, will affect all color records equally, since the color information is contained in the one emulsion layer unit, and so the color balance will be retained. A further distinction between the film and method of the invention and the prior art is that the light from the reflection mode scan does not pass through the image records, but passes through the color filter array then is reflected back through the array to the scanner. This is advantageous because the optical density range to be scanned is limited to that of the color filter array, typically a density of 1.5 in any one color, and so it is not necessary to use an excessively bright lamp.